Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/30—Inkjet printing inks
  • C09D11/32—Inkjet printing inks characterised by colouring agents
  • C09D11/322—Pigment inks
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/22—Compounds of iron
  • C09C1/24—Oxides of iron
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/42—Magnetic properties

Definitions

• the invention relates to ink-jet ink compositions, and more particularly to a process for the preparation of such ink-jet ink compositions suitable for use in the preparation of MICR documents. Specifically, the invention relates to aqueous ink-jet ink compositions containing extremely small particle size conductive metaloxides that have been treated to enhance performance and suspension parameters, and particular grinding, milling and filtration processing techniques to aid in the enhancement of the performance of such ink-jet ink compositions.
• aqueous ink-jet ink compositions contain a dye or pigment, a solvent system, which may be aqueous or non-aqueous in nature, and which may include a combination of various solvents or a single solvent, and various other components such as humectants, surfactants, dispersion aides, biocide or fungicide, and other components.
• solvent system which may be aqueous or non-aqueous in nature, and which may include a combination of various solvents or a single solvent, and various other components such as humectants, surfactants, dispersion aides, biocide or fungicide, and other components.
• inks suited for use in drop-on- demand and continuous print processing and which contain a conductive metal oxide component.
• These inks are generally categorized as magnetic inks, and may be used in various applications.
• One such application is the preparation of magnetic ink character recognition, or "MICR", readable documentation.
• MICR magnetic ink character recognition
• This type of application involves the use of magnetic ink to print all or part of a document, usually for security purposes.
• some "documents” where MICR readable ink compositions are used include checks, bonds, security cards, etc.
• MICR ink may be used to print an entire document, or only a portion thereof. For instance just the bar code region or only certain characters may be printed with MICR readable ink.
• the document once printed and subjected to an appropriate source of magnetization, is then passed through or under a MICR reading device, which validates or authenticates the document based on the MICR encoded characters or printed matter.
• the step of magnetizing the MICR ink once printed and before use imparts a specific magnetic charge to the magnetic component of the ink, causing an alignment of the particles.
• the particles must then retain the magnetic charge.
• the capability of a magnetic material to retain the imparted charge is referred to as remanence.
• this parameter increases with an increase in the particle size of the magnetic material. However, the larger the particle size the more difficult it is to maintain the particle in suspension within an ink composition.
• the print head nozzles of current ink-jet printers are very small, therefore the particulate matter in an acceptable ink-jet ink must be small in order to avoid clogging the nozzles, whether during printing or over an extended period of time. This need to maintain high remanence, but to decrease the particle size of the magnetic material to a very small size, presents a unique problem for potential MICR ink-jet ink manufacturers.
• the challenges of formulating a suitable ink-jet ink for use in MICR printing applications revolve around the need to achieve an ink composition containing very small particle size magnetic material, due to the size of the print head nozzles, and yet maintain the necessary level of remanence within the particulate matter in the ink such that the MICR readable characteristic of the ink is not compromised.
• Remanence is directly proportional to the size of the particle, thus decreasing the particle size of the magnetic material in order to avoid nozzle clogging of the print heads may also decrease the remanence parameter of the ink.
• One means of addressing a loss of remanence is to increase the magnetic component loading. This, however, is difficult due to the tendency of the particulate matter to settle out of solution as the amount of particulate matter in the ink composition is increased.
• USPN's 5,026,427, 5,240,626, and 5,656,071 each suggest the use of specific dispersants to maintain the suspension.
• the 5,656,071 patent discloses an ink composition including a polymeric dispersant to maintain a metal oxide in solution and a co-solvent mixture of 1,3-propanediol or 1,4-butanediol with a second solvent selected from polyethylene glycol-type materials and polyol/polyalkylene oxide condensates.
• the other patents involve the use of colloidally dispersed magnetite in conjunction with a specified dispersant component.
• USPN 5,240,626 discloses an ink including colloidally dispersed magnetite particles coated with a carboxy compound-type anti-agglomeration agent and a dispersing aid.
• the 5,026,427 patent teaches generally the preparation of a magnetic ink composition containing magnetic particles and specific dispersants to maintain the dispersion.
• Another means of addressing the suspension issue is set forth in USPN 4,026,713. This patent discloses the use of a combination of surfactants and glycerol to make stable magnetic inks.
• Yet another means of addressing the suspension problem of magnetic inks has been the use of resin components to enhance the oxide suspension.
• USPN's 5,547,804, 5,670,078, and 5,969,003 are examples of this type of response to the problem.
• the challenges of formulating a suitable ink-jet ink for use in MICR printing applications revolve around the need to achieve an ink composition containing very small particle size magnetic material, due to the size of the print head nozzles, and yet maintain the necessary level of remanence within the particulate matter in the ink such that the MICR readable characteristic of the ink is not compromised.
• the invention relates to a means of achieving the foregoing challenge.
• One aspect of the invention relates to a process for the preparation of an aqueous MICR ink-jet ink composition
• a process for the preparation of an aqueous MICR ink-jet ink composition comprising a metal oxide dispersion and a suitable ink-jet ink formulation, the dispersion comprising metal oxide particles of very small size, less than about 0.5 ⁇ , wherein the preparation process includes preparing the metal oxide pre- dispersion and then grinding the pre-dispersion to reduce the size of the magnetic oxide particles prior to the addition of the pre-dispersion to the remaining ink-jet ink formulation components.
• Yet another aspect of the invention relates to a process for the preparation of a MICR ink-jet ink composition
• a MICR ink-jet ink composition comprising a metal oxide dispersion and a suitable ink-jet ink formulation, the dispersion comprising metal oxide particles of very small size, less than about 0.5 ⁇
• the preparation process includes preparing the metal oxide pre-dispersion and then grinding the pre-dispersion using a combination of conventional and non- conventional grinding techniques to reduce the size of the magnetic oxide particles and to reduce the potential for particle agglomeration.
• Still another aspect of the invention relates to a process for the preparation of a MICR ink-jet ink composition
• a process for the preparation of a MICR ink-jet ink composition comprising a metal oxide dispersion and a suitable ink-jet ink formulation, the dispersion comprising metal oxide particles of very small size, less than about 0.5 ⁇ ,prepared by first obtaining a suitable metal oxide pre-dispersion, and then grinding and filtering the pre-dispersion to reduce the size of the magnetic oxide particles and to reduce the potential for particle agglomeration.
• the filtering process may involve the use of a single filter or may involve the use of a step-down filtration regimen.
• the invention relates to the use of particular processing techniques for the purpose of achieving a metal oxide pre-dispersion containing extremely small particle size metal oxides which remain in suspension over an extended period of time and the use of the same pre-dispersion in aqueous MICR ink-jet ink compositions.
• processing techniques for the purpose of achieving a metal oxide pre-dispersion containing extremely small particle size metal oxides which remain in suspension over an extended period of time and the use of the same pre-dispersion in aqueous MICR ink-jet ink compositions.
• MICR ink-jet ink prepared in accord with one or more of the processing techniques described herein does not exhibit any tendency to clog the small nozzles of the ink-jet print head, despite the particulate content of the ink.
• An ink-jet ink composition meeting the foregoing criteria comprises a metal oxide pre-dispersion which is mixed with an ink-jet ink formulation containing conventional ink-jet ink components.
• This dispersion includes specific metal oxide components that have been specially prepared in order to achieve the desired performance. This preparation involves subjecting the pre-dispersion to conventional and/or non-conventional grinding techniques, and may be further subjected to particular filtration techniques to achieve the smallest particle size without experiencing agglomeration. The dispersion once processed in this manner may then be included in an ink-jet ink composition suitable for use in MICR applications.
• Magnetic iron oxides in conventional MICR transfer application coatings typically exhibit a size of 2.0 ⁇ (microns) or larger. Since these coatings consist of a dried film containing iron oxide, binders and oils, the iron oxide is held in the dried binder matrix, after the solvent is evaporated. Therefore, settling problems are not an issue.
• the magnetic iron oxide used in MICR ink-jet applications differ from these conventional MICR coatings due to the fact that the ink-jet ink format requires the use of an aqueous ink composition.
• the iron oxide intended for use in MICR ink-jet applications must be produced in smaller particle size than conventional applications, such as conventional drop-on-demand and thermal transfer coatings, because it must pass through the much smaller orifices characteristic of ink-jet print heads.
• the metal oxide must exhibit and retain the proper magnetic properties (as the magnetic particle size decreases the magnetic properties in general will deteriorate with time), must have good dispersibility within aqueous liquid systems, and must have good hydrophillic suspension properties. These properties are not as stringently required with conventional MICR applications that are based on non-aqueous solvent suspensions or hot melt wax technologies.
• Oxides suitable for ink-jet applications must be extremely fine in particle size without experiencing the usual loss of magnetic properties inherent in size reduction of magnetic particulate matter.
• Suitable ink-jet oxides must also be hydrophillic in nature in order to provide good dispersion characteristics, and to provide good emulsion properties. The latter parameters relate directly to the ability of the oxide to exhibit minimum settling and to further demonstrate the proper wetting of the oxide with the other water-soluble ingredients generally present in an ink-jet ink composition.
• MICR ink-jet inks Another concern in the formulation of MICR ink-jet inks as opposed to conventional MICR inks presents itself in the form of the ink, i.e., MICR ink-jet inks must be fluid, and not dry. Because iron oxide has a specific gravity of approximately 5 it has a natural tendency to settle to the bottom of a fluid ink composition, resulting in a non- homogenous fluid having an iron oxide rich lower layer and an iron oxide deficient upper layer. Therefore, a main challenge in developing MICR ink-jet ink is keeping the iron oxide homogeneously suspended in the fluid ink composition, and having the size of the iron oxide particles small enough to pass through the orifices of an ink-jet print head.
• the iron oxide must also meet the requirement of having sufficient magnetic signal strength to be readable in MICR reader/sorter equipment, such as that employed by the banking industry. Achieving sufficient signal strength becomes increasingly difficult as the metal oxide particle size diminishes and the practical limits on percent content of metal oxide in the ink composition are reached.
• the magnetic property that is most important is remanence, which should be at least a minimum of 25 emu g. The higher the remanence value the stronger the readable signal. A particle exhibiting higher remanence will require less total percent iron oxide in the ink formula and will improve the suspension properties over an ink formula containing a particle with lower remanence used at a higher percent iron oxide content.
• magnetite or synthetic magnetic iron oxide is the preferred magnetic component for MICR ink-jet ink applications, there are other materials that may also be employed. Any reference to an iron oxide component is equally applicable to these other metal oxides and metal-containing compounds.
• cobalt and/or manganese may be substituted in part for the iron component in the oxide compound to yield bi- or tri- metallic materials with the proper magnetic properties.
• Chromium complexes which are used in the audio and video tape industry are another possible example.
• Another example is neodymium-iron-boron-lanthanum (NdFeBLa) powder as supplied by UltraFine Powder Technology of Woonsocket, R. I. Additionally, compounds without any iron content provide another possibility.
• Such materials include, but are not limited to, certain copper germanium oxide and vanadium oxide complexes.
• Yttrium manganese hydrogen has magnetic properties and compounds where the yttrium is substituted with rare earth elements (Gd, Tb, Dy, Ho) may also be used.
• MICR ink-jet ink must also exhibit low viscosity, typically on the order of less than about 5cps and more preferably on the order of about l-2cps, in order to function properly in both drop-on-demand type printing equipment, such as thermal bubble jet printers and piezoelectric printers, and continuous type print mechanisms.
• low viscosity fluids adds to the concerns of successfully incorporating metal oxides into the ink solution because particle settling will increase in a low viscosity, thinner fluid as compared to a more viscous, thicker fluid.
• metal oxides were evaluated with regard to their suspension properties. All metal oxides evaluated were iron oxide compounds. Use of the same base metal oxide, but in different forms and with various coatings provided a more accurate comparison of the affect of these parameters on the settling/suspension properties of metal oxides. In conducting this evaluation, each of the following oxides was used to formulate a 10% suspension in water, wherein the iron oxide pigment was slowly added to water followed by 10 minutes of high speed mixing. These suspensions were then allowed to settle. Table I sets forth the results of this evaluation.
• Example No. 2 and No. 4 iron oxide in the dry and wet cake form, respectively
• Example No. 12 small particle size iron oxide
• Examples 2 and 4 were coated with aluminum silicate. This hydrophillic coating imparts to the oxide particles a tendency to remain as separate particles with less tendency to agglomerate.
• Example No. 12 had the smallest particle size of any oxide tested, measuring a mean particle size of 0.13 ⁇ . This oxide also exhibited good remanence ( ⁇ 28-29 emu/g), and had a hydrophillic surface coating to promote good dispersibility in an aqueous medium.
• inorganic silicates such as sodium silicate, potassium silicate, cupric silicate and other inorganic silicates may be employed.
• hydrophillic coatings such as metallic stearates, metallic phosphate esters, metallic sulfonites and other similar compounds may also be used to coat metal particulate components with good results.
• MICR ink-jet ink gives rise to yet another unique consideration, in addition to that of choosing a suitable oxide component.
• This consideration revolves around the difficulty in obtaining a good dispersion.
• One reason for this difficulty is the high density of the iron oxide material and the inherent tendency of the oxide to settle out of solution.
• a hydrophilic surfactant or a combination of surfactants are substances that function to increase the spreading and wetting properties of a liquid, and usually reduce the overall viscosity and surface tension of the liquid.
• the surface-active molecule must be at least partly hydrophilic when being incorporated into an aqueous liquid medium. Therefore, a particular type of molecular structure readily lends itself to use as a surfactant.
• This molecular structure includes a water- soluble or hydrophilic component, and a water insoluble or hydrophobic component.
• the hydrophobe is usually the equivalent of a hydrocarbon having from about 8 to 18 carbons, and can be aliphatic, aromatic, or a mixture of both.
• the sources of hydrophobes are normally natural fats and oils, petroleum fractions, relatively short synthetic polymers, or relatively high molecular weight synthetic alcohols, and the like.
• the hydrophilic groups give the primary classification to surfactants, and are categorized as anionic, cationic or non-ionic in nature.
• the anionic hydrophiles generally belong to a group including carboxylates (soaps), sulphates, sulphonates, phosphates, and the like.
• the cationic hydrophiles are generally a form of an amine product.
• the non-ionic hydrophiles associate with water at the ether oxygens of a polyethylene glycol chain.
• the hydrophilic end of the surfactant is strongly attracted to the water molecules of an aqueous solution.
• the force of attraction between the hydrophobic component of the surfactant and the water is only slight.
• the surfactant molecules align themselves at the surface and internally so that the hydrophile end is oriented toward the water and the hydrophobe is oriented away from the water.
• This internal group of surfactant molecules is referred to as a micelle.
• Dispersants are surfactants that suspend a solid in water or some other liquid, this instance, the surfactant functions to form what amounts to a protective coating around the suspended material, and the hydrophilic ends associate with the neighboring water molecules.
• the particle size and density of the suspended material also affect the stability of the suspension. Therefore, each factor must be addressed to achieve a desired result.
• MICR ink-jet ink Dispersions As was stated previously, it has been determined that one manner of achieving a MICR ink-jet ink with suitable magnetic properties is to first prepare a metal oxide pre- dispersion which can subsequently be used to formulate the MICR ink-jet ink.
• This dispersion will include the specific metal oxide components, specially prepared with regard to particle size, remanence, and coatings, in conjunction with an aqueous medium containing a surfactant component.
• particular grinding techniques may be used to reduce the size of the individual magnetic oxide particles and to reduce particle agglomeration so that the particles can freely pass through the very small orifice openings characteristic of ink-jet print heads.
• One method to reduce the particle size of the metal oxides is to use conventional grinding techniques, such as ball milling. This type of technique is time dependent, i.e., the longer the dispersion is subjected to the grinding process the smaller the particle size that can be achieved.
• a second method that is suitable for use in decreasing the particle size of the metal oxides in the dispersion is the use of non-conventional grinding methods combined with and employed as a post-grinding scheme after the use of conventional grinding means. Additionally, a step-down filtration method may be employed to achieve the desired small particle size.
• Tamol 731 A (Surfactant) 2.00%
• This dispersion was prepared by adding the iron oxide pigment to an aqueous solution slowly with continued high speed mixing, for about 10-15 minutes. This mixture was then mixed for 2 hours on a Roller Mill without any grinding media. This dispersion, when measured on a Hiriba particle size measurement instrument, exhibited a mean particle size of 0.871 ⁇ and a maximum particles size of 3.409 ⁇ .
• the sample thus prepared was then put into a ball mill with V" steel balls and milled for 4 days. After this milling process the dispersion was diluted down from 44% solids to 30%) solids with distilled water.
• the sample now had the following values when measured on the Hiriba instrument: mean particle size of 0.504 ⁇ and a maximum particle size of 1.318 ⁇ . Therefore, the 4 day ball mill grinding process reduced the mean particle size by - 0.367 ⁇ and the maximum particle size by -2.083 ⁇ .
• Dispersion 2 Another example of this type of processing on an ink-jet dispersion containing iron oxide pigment is set forth hereinbelow.
• the iron oxide pigment used was a dry particulate coated iron oxide consistent with that noted in Table I, Example 2.
• This dispersion was prepared in the same manner as Dispersion 1, was processed in a ball mill with V4" steel balls and milled for a period of 4 days, and was then diluted down from 44% solids to 30% solids with distilled water.
• Dispersion 2 Coated Iron Oxide 40.00%
• Dispersion 2 As with Dispersion 1, the mean and maximum particle sizes for Dispersion 2 were measured using a Hiriba instrument. The mean particle size for the original dispersion was 0.450 ⁇ , with a maximum particle size of 1.151 ⁇ . In comparing these measurements with those rendered from Dispersion 1, which was processed under identical conditions, it was noted that Dispersion 2 exhibited a smaller mean and maximum particle size. This difference was attributed to the inherent smaller particle size of the iron oxide used to make the dispersion. Dispersion 2 was also processed in a microfluidizer under the same conditions as Dispersion 1, and was passed through the same series of filters as used to evaluate Dispersion 1. The results of the series filtration showed an 88.20% solids yield through 20 ⁇ , 6 ⁇ , and 3 ⁇ filter series.
• the dispersion may be incorporated into an ink composition suitable for use in ink-jet printing equipment.
• the precise formulation for the ink is dependent to some degree on the type of print engine the ink will be used in, i.e., drop- on-demand or continuous, but in general the ink-jet ink will include some or all of the conventional ink-jet ink components. Among these components are colorants, humectants, dye or pigment stabilizers, surfactants, buffering agents, biocides, and water-soluble resins, to name a few.
• the ink-jet ink including the metal oxide dispersion prepared as specified herein was loaded into an HP45A cartridge and tested in an HP 895 ink-jet printer.
• the HP45A cartridge was filled with the MICR ink-jet ink, and the print output font was configured with ANSI MICR specified characters on an IBM compatible computer.
• the printing media used was standard check stock. MICR characters were generated on the check stock and evaluated for proper MICR performance per ANSI standards with an RDM MICR verifier.
• Dispersion 1 (40% oxide; ball milled for 4 days) 35.00
• the ink-jet ink formulated according to the above recipe was placed in an HP45 A cartridge and the machine was operated to generate the printing of 45 MICR characters on MICR card stock. The MICR characters were then evaluated on an RDM MICR Verifier and exhibited a Document Average Signal Level of 87% and 41/45 characters were clearly MICR readable.
• Drop-On-Demand Ink- Jet Ink Formulation B Another ink-jet ink composition including a metal oxide dispersion prepared in accord with the invention herein was formulated. This ink-jet ink formulation, Formulation B, was similar to the first formulation, Formulation A, but used a dispersion that had been subjected to additional grinding and filtration. This ink was filtered just as the Formulation A ink was filtered, but then was further filtered by passing through a Fisher P8 filter.
• MICR Ink- Jet Formulation B
• Dispersion 1 (30% oxide; ball milled for 4 days and 50.00 micronized)
• the Formulation B Ink- Jet Ink was tested in accord with the testing performed on Formulation A and demonstrated a Document Average Signal Level of 89% and exhibited 44/45 characters that were MICR readable.
• the printed characters for this Formulation B displayed increased sharpness as compared to the characters printed from the Formulation A Ink- Jet Ink. This is attributed to the additional milling and filtration procedure used in developing this sample.
• the ink-jet ink formulations including the metal oxide dispersion prepared in accord with the processing set forth herein, were also tested in continuous type print equipment.
• a continuous ink-jet print head set-up was prepared.
• the system was a continuous recirculating flow system that allowed for the evaluation of jetting properties of the ink through the individual print head nozzles under continuous use.
• the print head system was set up as a generator for the ink stream through the individual nozzles. There was no deflection unit.
• the individual ink streams through the nozzles were evaluated with a lighted magnifying inspection light for straightness of each ink stream going through each nozzle. Any curvature of a stream or blockage of a nozzle was noted.
• the system was monitored under pressure and any change to the pressure was noted. There were two filters in line in the system.
• This formulation was ball milled for 4 days and diluted to 15% solids with distilled water. The formulation was tested on the continuous print set-up as described above.
• the ink started jetting at 10 psi but exhibited partial print head nozzle blockage after 15 minutes with pressure of 14 psi and by 30 minutes was experiencing total print head nozzle blockage at a pressure of greater than 30 psi.
• Formulation C (ball milled for 4 days) 25.00

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• Inks, Pencil-Leads, Or Crayons (AREA)

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• 2002
  • 2002-07-01 US US10/186,440 patent/US6767396B2/en not_active Expired - Lifetime
• 2003
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  • 2003-05-12 WO PCT/US2003/014910 patent/WO2004003088A1/fr not_active Ceased
  • 2003-05-12 CA CA002491643A patent/CA2491643A1/fr not_active Abandoned
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